Dolphins

The Australian snubfin dolphin (Orcaella heinsohni, ‘snubfin dolphin’ hereafter) and Australian humpback dolphin (Sousa sahulensis, ‘humpback dolphin’ hereafter) are poorly-understood species of dolphin whose global distribution is restricted to shallow coastal and estuarine waters of northern Australia and southern New Guinea.

Here, we investigate the population genetic structure and relative abundance of these two species at selected study sites in the Kimberley region of north-western Australia. Additionally, we investigate the application of passive acoustic monitoring (PAM) as an effective technique for monitoring these species in the remote waters of the Kimberley region, with potential applications across northern Australia.

Population genetic structure: Collect tissue samples from free-ranging dolphins and use nuclear and mitochondrial genetic markers to examine population genetic structure and gene flow between several locations within the Kimberley region.

Relative abundance: Conduct boat-based surveys and photo-identification to obtain information on species composition, group size and composition, and encounter rates of snubfin and humpback dolphins at several locations in the Kimberley region.

Use small vessels as platforms for visual surveys of dolphins, collecting data on location, behaviour and group composition of dolphins, in addition to high quality image of dorsal fins for individual identification purposes (photo-ID). Obtain small skin/tissue samples from free-ranging dolphins using a remote biopsy darting system. Samples will subsequently be analysed to determine sex and measures of gene flow between populations from nuclear and mitochondrial DNA markers.

Deploy compact acoustic recorders on temporary moorings to record dolphin vocalisations in parallel with visual observations from an elevated observation platform (moored ship in Roebuck Bay; elevated land in Cone Bay).

Data collection at the Prince Regent River was facilitated by collaboration with the Dambimangari-Parks and Wildlife Joint Management Team for Lalang-garram/Camden Sound Marine Park.

Outcomes

This project and related work within the region has resulted in a variety of outcomes of potential use to managers and scientists; these include:

Improved understanding of the distribution and relative abundance of snubfin and humpback dolphins at several remote locations in the Kimberley, assisting in the identification of important habitats, management of threats and providing a benchmark for future research and monitoring in the region.

An improved understanding of the genetic connectivity of snubfin and humpback dolphin populations in north-western Australian waters and the appropriate geographic scales at which to manage them.

Characterisation of the underwater soundscape at two locations in the Kimberley.

Illustration that PAM provides a method of effectively detecting snubfin and humpback dolphins in high-use areas, and an increased information base from which to further develop PAM towards more quantitative and species-specific monitoring.

Results which will assist in the identification of important habitats, management of threats and which provide a knowledge base for future research and monitoring in the region.

Development of positive and effective relationships and collaborations between researchers, indigenous rangers and regional wildlife management staff.